Three-dimensional laser holographic interferometry measurements.

摘要

This research develops new methods to improve the laser holographic interferometry for the three dimensional (3D) non-contact optical precision measurement of manufactured components, such as engine heads and blocks, automatic transmission valve bodies, precision journals, and wheel hubs and rotors. These components usually have large size, tight dimensional and geometrical form tolerances, and short manufacturing cycle time. Effective and flexible 3D non-contact optical methods for the accurate, fast and full surface measurement of these precision components are still unavailable.; A hologram registration method without using targets is developed for the laser holographic interferometry measurement of objects larger than the field of view (FOV). This method is validated using a wheel hub smaller than the FOV and demonstrated using an engine head larger than the FOV.; A phase unwrapping method is developed to mathematically increase the height measurement range of the laser holographic interferometry while maintaining the same accuracy and resolution. This method successfully solves the phase unwrapping problem of laterally discontinuous surfaces and is validated using an automatic transmission valve body.; A mathematical method is developed to utilize the laser holographic interferometry with customized optical and mechanical configurations for flexible and full surface measurement of cylinders with variable diameters. The simulations show that this method evaluates the cylindricity with good accuracy and the experiment demonstrates its feasibility.; A preliminary study is conducted to analyze the flatness evaluation errors for high definition measurements. Two commonly used methods, least square and minimum zone, with three flatness definitions, are analyzed. The least square method with the modified peak-to-valley definition demonstrates good potential to effectively evaluate the flatness for the high definition measurement system.; The future work of this research is aimed in two areas. First is to improve the cylindricity measurement method by developing the calibration of the cylindrical lens and enhancing the estimation process of the system configuration parameters. Second is to develop a more comprehensive method to analyze the flatness measurement errors for high definition measurements and extend it to other complicated geometrical forms.